1. Field of Invention
This invention relates to heat exchangers used in space conditioning systems, such as air conditioners and heat pumps, and in particular to a device for preventing direct contact between a heat exchanger made of a first type of metal and a cabinet in which the heat exchanger is located and which is made of a second type of metal.
2. Background Art
In one type of space conditioning system known as a central air conditioning system, the system is comprised of an indoor unit and an outdoor unit. The indoor unit includes a first heat exchanger used as an evaporator for evaporating a phase change refrigerant and an air handler having a blower for blowing indoor air to be cooled across the first heat exchanger. The outdoor unit includes a second heat exchanger used as a condenser for condensing the vapor refrigerant evaporated in the first heat exchanger and a compressor for compressing the vapor refrigerant before it enters the second heat exchanger and for circulating refrigerant between the first and second heat exchangers.
Another type of space conditioning system known as a heat pump system also includes an indoor unit and an outdoor unit. Heat pump systems operate similar to the central air conditioning system described hereinabove, except that a heat pump system can be used for both cooling and heating. Both of the heat exchangers can function as an evaporator or a condenser, depending on whether the heat pump system is being operated in a heating or cooling mode. For example, if the heat pump system is being operated in a heating mode, the heat exchanger in the outdoor unit functions as an evaporator and the heat exchanger in the indoor unit functions as a condenser. If the heat pump system is being operated in the cooling mode, the heat exchanger in the indoor unit functions as an evaporator and the heat exchanger in the outdoor unit functions as a condenser.
According to prior practice, heat exchangers used in space conditioning systems typically include one or more refrigerant carrying copper tubes laced through plural relatively thin, aluminum fins. The tubes extend between steel inlet and outlet headers and the heat exchanger is mounted by attaching the steel headers to a steel cabinet or the like. Because the heat exchanger headers are made of the same material as the cabinet with which the heat exchanger is mounted, galvanic corrosion is normally not a major problem. However, other types of heat exchangers are known in the art that have application in space conditioning systems. Such other heat exchangers include so-called xe2x80x9cparallel flowxe2x80x9d heat exchangers in which both the tubes and headers are made of aluminum. The tubes are typically flat with relatively small hydraulic diameter flow paths inside each tube. When aluminum heat exchangers of this type are mounted with a steel cabinet, the dissimilar metals may result in unacceptable levels of galvanic corrosion in the heat exchanger. Therefore, there is a need to isolate the aluminum heat exchanger from the steel cabinet in which the heat exchanger is mounted, to prevent direct contact therebetween.
In accordance with the present invention, isolation means is provided for isolating a space conditioning system heat exchanger made of a predetermined first type of metal from a cabinet made of a predetermined second type of metal with which the heat exchanger is mounted. In accordance with a feature of the invention, the isolation means includes at least one first non-metallic member located on a top part of the heat exchanger to prevent contact between the heat exchanger and a top part of the cabinet and at least one second non-metallic member located on a bottom part of the heat exchanger to prevent contact between the heat exchanger and a bottom part of the cabinet. In accordance with another feature of the invention, the heat exchanger includes at least one mounting bracket made of the first type of metal and located on at least one end of the heat exchanger. The isolation means further includes at least one third non-metallic member interposed between the mounting bracket and an attachment member made of the second type of metal, which is used to mount the heat exchanger with the cabinet, to prevent direct contact between the attachment member and the bracket.
In the preferred embodiment, the first type of metal is aluminum and the second type of metal is steel. The first non-metallic member includes plural-snap fit plastic members spaced along the top part of the heat exchanger and the second non-metallic member also includes plural-snap fit plastic members spaced along a bottom part of the heat exchanger. The third non-metallic member preferably includes at least one plastic bushing adapted to extend between aligned holes in the mounting bracket. The bushing is adapted to receive the attachment member therethrough and prevents direct contact between the attachment member and the mounting bracket. Plural mounting brackets are preferably located on each end of the heat exchanger.
In accordance with the present invention, a device is provided for isolating a heat exchanger made of a first type of metal (e.g., aluminum) from a cabinet made of a second type of metal (e.g., steel) with which the heat exchanger is mounted. Corrosion due to galvanic action between dissimilar metals is effectively controlled by preventing direct contact between the heat exchanger and cabinet, while allowing the heat exchanger to be mounted in a fixed position within the cabinet.